Did you miss the part where it could be activated remotely, and was modified remotely in an attempt to conceal its nature as a political tool? As we've seen with the US, governments will do anything they think they can get away with. Making it known that even the tiniest millimetric step in this direction with not be tolerated is extremely important as the West's tech landscape is occupied more and more by Chinese devices, Chinese software, and Chinese algorithms.
Updating any smart phone to the same functionality over the air would be trivial though.
So if you were the Chinese government wanting to stop those phrases being used at some time in the future, it would make more sense to send the list at the time you activate the list, rather than in advance to be found before it's ever been activated.
It's tempting to assume incompetence but I'll go with the following: they might be testing the waters and check if the Western society is vigilant and reacting to their actions.
Hundreds of generic "naughty" words were added to the list remotely by Xiaomi in order to make the list seem like it wasn't intended as a political tool, then Xiaomi remotely deleted it from the phone.
